I'll suggest the reader of this review to go through plot-summary of this novel and a little familiariation with its prequel, 2001: A Space Odyssey. I'll only be expatiating here on some aspects I found fascinating.
Although, the novel contains many captivating sub-plots and a driving, gripping backdrop; I want to credit Arthur C Clarke for the most wonderful depictions of the Jovian system. Within the first half, he describes the bands of Jovian clouds, the cyclonic storms, the radiation belt and the high-energy electron beam connecting Io to Jupiter; he depicts Io, a land of fiery volcanoes, violent eruptions making umbrella clouds and molten lava lakes; and he uses all the available information about Callisto, Ganymede and Europa to paint a vivid and entrancing picture of the moonscapes using his never-exhausting arsenal of beautiful, sublime metaphors. Perhaps, Clarke's level of ingenious and prolific depiction of the real planets and satellites could only be matched by none other than the Great Carl Sagan.
I give Clarke enormous credit and due respect for not weaving mystical and unreal, speculative scenery of the worlds, but instead relying on the available information to show such a scenario that could possibly never be imagined by any of the Earth-bound fantasy writers. It is true, that the Universe is not stranger than we imagine, but it is stranger than we can imagine.
Also, it turns out that the strange, eerie, surreal and enigmatic Universe is actually much more profoundly beautiful and enchanting than we can possibly imagine.
However, Clarke does resort to speculation in the latter half when he begins to describe the non-corporeal Dave Bowman's descent into sub-surface Europa to look for indigenous life and his descent into Jovian atmosphere to look for gaseous life, metallic hydrogen and the diamond core as big as the Earth. These speculations still stand on the solid ground of research and inferential hypotheses propounded by reputable scientists. However, the climax of Jupiter condensing and initiating nuclear fusion is absolutely speculative fantasy and couldn't be given much serious consideration, even though the condensation is said to be trigerred by higher forms of technological intelligence.
I should point out that, in the prequel, Dave Bowman was converted by the invisible masters of the Galaxy into a pure-energy life-form, retaining his memory and consciousness. The invisible masters are the entities which look for developing intelligence across the Galaxy and then ensure its survival and development by setting up dark rectangular slabs which direct the life-forms and protect them. This patronizing sort of intelligence occurred to me as highly disturbing and rather unsettling one; this hypothesis regards humans as highly vulnerable to self-destruction and incapable of supporting themselves against the follies and vices they commit, threatening their prospects of survival in consequence. Which is obviously true, but I find my own ideas to be better in sync with those of Isaac Asimov and Carl Sagan which hold the belief in human intelligence, our ability to overcome our weaknesses and the potential of conquering the cosmos without needing any sort of external intervention.
It also occurs to me that despite being a close friend of Carl Sagan, Clarke was highly inclined towards theistic philosophies and his idea, showing invisible masters guarding and helping the intelligences, can be said to be the manifestation serving his purpose of having deities in real world.
His description of HAL 9000, the self-conscious artificial intelligence aboard Discovery, and the treatment it is subjected to, raises many questions and concerns about our ethics of dealing with non-human, non-organic intelligence. The crew never regards HAL as a person, and they stand at a ready to dissipate it in case it disobeys them, they even abandon HAL to save themselves while running from Jovian collapse and ignition. Clarke's HAL talks and behaves distinctively like a person, it shows efforts for self-preservation and even subdued fear. But Clarke doesn't go into details about it unlike his contemporary, Isaac Asimov. It holds imperative that we review our understanding and ethics about treating other forms of consciousness, robots, computers and even animals in a better and compassionate way.
It is rather a hard-science fiction novel, relying almost exclusively on pure scientific facts and inferences, and almost negligibly on unrealistic speculations. His description of space travel, the environment aboard the ship, interactions and relationships of the crew; are satisfying.
Clarke is a master at weaving dark, haunting atmospheres which always show his cynicism and impart fear and thrill into reader's mind. He succeeds superbly at it, while describing the anxiety, fear, stress and agony of the crew whose characters are otherwise, at best, a little more than single-layered caricatures.